As a general rule, sensors for the measuring of analyte concentrations of bodily fluids such as, e.g., blood or interstitial fluids cannot be manufactured with exactly preset measuring sensitivities. Typically, considerable deviations occur between production batches. To determine analyte concentrations by means of sensor signals provided by in-vivo measurements with sufficient exactitude for medicinal applications, calibration data are therefore required that were either determined at the pertinent sensor itself or by means of random testing of other sensors of the pertinent production batch. In general, such calibration data describe the difference between an ideal sensor sensitivity and a determined sensor sensitivity.
Systems for the in-vivo measurement of analyte concentrations typically comprise exchangeable sensors as exchange or consumable components and a long-life base station to which the exchangeable sensors are connected. This brings about the problem that at each exchange of sensor, new calibration data must be made available to the system.
Calibration data can be made available on a packing leaflet for the sensor and be manually entered by the user into the system. Because this procedure entails, however, the danger of input errors it is more beneficial to accompany each sensor or each sensor package with a data carrier with thereto stored calibration data in order to preclude the risk of input errors.
However, also this solution is not perfect since the risk exists that data carriers associated with different sensors could be transposed by the users and erroneous calibration data would thus be made available to a system which, in turn, would cause erroneous measuring results.
The sensors of an in-vivo measuring system must be sterile because they are inserted into the body of a patient. When being packaged together with a data carrier in a single housing, the customary method of sterilization, to wit, an intensive irradiation, entails considerable difficulties. Because electronic or magnetic data carriers are impaired due to the required radiation dose required for sterilization, it is not possible, or only with very expensive, especially manufactured data carriers, to irradiate the sealed housing with the therein arranged sensor and data carrier to sterilize the sensor.